socket.io/lib/util/json.js

// Based on JSON.js from MooTools (MIT)
// Copyright (c) 2006-2009 Valerio Proietti, <http://mad4milk.net/>

(function(){

  var array = io.util.Array,
      special = {'\b': '\\b', '\t': '\\t', '\n': '\\n', '\f': '\\f', '\r': '\\r', '"' : '\\"', '\\': '\\\\'},    
      json = io.util.JSON = {},

  escape = function(chr){
    return special[chr] || '\\u' + ('0000' + a.charCodeAt(0).toString(16)).slice(-4);
  },

  isSecure = function(string){
  	string = string.replace(/\\(?:["\\\/bfnrt]|u[0-9a-fA-F]{4})/g, '@').
  					replace(/"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g, ']').
  					replace(/(?:^|:|,)(?:\s*\[)+/g, '');
	
  	return (/^[\],:{}\s]*$/).test(string);
  };

  json.encode = JSON.stringify || function(obj){
  	if (obj && obj.toJSON) obj = obj.toJSON();
	
  	if (obj === null){
  	  return 'null';
  	}
	
  	if (obj instanceof Array){
  	  return '[' + array.map(obj, JSON.encode) + ']';
  	}
		
  	switch (typeof obj){
  		case 'string':
  			return '"' + obj.replace(/[\x00-\x1f\\"]/g, escape) + '"';
  		case 'object':
  			var string = [];
  			for (var key in obj){
  				var json = JSON.encode(obj[key]);
  				if (json) string.push(JSON.encode(key) + ':' + json);
  			}
  			return '{' + string + '}';
  		case 'number': 
  		case 'boolean': 
  		  return '' + obj;
  	}
	
  	return null;
  };

  json.decode = function(string, secure){
  	if (!string || typeof(string) != 'string') return null;
	
  	if (secure || JSON.secure){
  		if (JSON.parse) return JSON.parse(string);
  		if (!isSecure(string)) throw new Error('JSON could not decode the input; security is enabled and the value is not secure.');
  	}
	
  	return eval('(' + string + ')');
  };

})();